Spanish Slug

Fascinating facts about the Spanish Slug

• The adult Spanish slug can stretch up to 140 mm long, yet looks just like its close cousin Arion rufus, forcing scientists to slice open the animal to check its genitalia. Juveniles give a clue: only A. vulgaris sports longitudinal bands on its skin.
• First spotted in Britain in 1954, the Spanish slug has marched across Europe year after year, France by 1955, Sweden by 1975, and even reached Canada in 2009. Its Asian foothold appeared only recently, with confirmed finds in Armenia and Russia in 2022. This relentless clockwork expansion shows how a single misidentified species can colonise continents, turning local gardens into battlegrounds and threatening native ecosystems far beyond its original home.
• A single Spanish slug can lay about 400 eggs in its lifetime, each clutch averaging 70 eggs tucked up to 10 cm underground or on the soil surface. Mating kicks off in July, eggs are deposited in late summer, and hatch from autumn to spring, but any eggs or slugs hit below, 3 °C simply die.
• When conditions are right, Spanish slugs can pack 50 individuals into a single square metre, sometimes even more, munching everything from tender seedlings to dead conspecifics. Their appetite extends to seeds, which they destroy far more often than other gastropods, slashing future plant growth. In Sweden, such feeding pressure has led to complete defoliation of native shrubs in natural woodlands, illustrating how sheer numbers can reshape entire plant communities.
• Ranked among Europe's 100 worst invasive species, the only land gastropod on that list, the Spanish slug can start a new invasion from a single hermaphroditic individual because it can self-fertilise. One slug hitching a ride on garden waste can seed a whole population, threatening agriculture, native wildlife and even human health. Its status as a top quarantine concern in the USA underscores how a tiny, self-sufficient mollusk can become a global pest.

Sources

Every fact above was checked against these pages, and kept only where one of them states it.

• Wikipedia

At a glance

About the Spanish Slug

In the damp, moonlit gardens of the Iberian Peninsula, the Spanish Slug emerges as a silvery, nocturnal phantom, its undulating body leaving a glistening trail of slime in its wake as it navigates the intricate network of leafy hideaways and forgotten pathways. With a quiet, relentless purpose, it devours the tender shoots and leaves of its host plants, its very existence a testament to the enduring power of adaptation and resilience in the natural world. As it moves, its antennae twitching like delicate feelers, the Spanish Slug embodies a strange, slow-motion beauty, a reminder of the secret lives that unfold beneath our feet.

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